Styrene-based resin have excellent water-resistance, mechanical strength and moldability and used in many application fields as parts of household and office appliances as well as construction materials. The material used in such application fields must pass a flame retardancy standard established for each application field. These standards have become severer for safety reason against fire. For example, the regulation under the UL standard (Underwriters Laboratories, U.S.A.) for household and office electrical appliances has become more stringent in recent years.
Flammable styrene-based resins need be flame-retarded in a variety of ways under these circumstances. Most practical and effective way is, among others, to incorporate a brominated flame retardant.
It may be possible to pass the stringent flame retardancy standard by increasing the amount of brominated flame retardant to be added to the resin. However, this approach is not only uneconomical but may adversely affect the generation of harmful gas and the mechanical properties. It is desirable to render the resin flame-retarded with as small as possible amount of the flame retardant.
We have found that certain phthalocyanine-metal complexes enhance the flame retardancy of a brominate flame retardant (a flame retardant containing at least 50 wt % of bromine). It has been proposed in the past to incorporate a phthalocyane-metal complex to flammable plastics in conjunction with the brominate flame retardant for different purposes.
For example, JP2000/239461A discloses addition of phthalocyane blue (copper phthalocyanine) to flame-retarded polypropylene as a blue colorant. U.S. Pat. No. 3,825,520 discloses that when a metal (Fe, Cu, Mn, V and Co) phthalocyanine is incorporated to flame-retarded polystyrene or ABS composition containing octabromobiphenyl, smoking of the composition during burning is reduced. JP 9/255879A teaches that when adding ultrafine particles of a metal coordination compound, thermoplastics including polystyrene may be rendered flame-retarded effectively with a small addition of a flame retardant. However, phthalocyanine is not disclosed as the ligand of the coordination compound.